1. 1 WRF-EnKF Lightning Assimilation Real-Observation Experiments Overview Cliff Mass, Greg Hakim, Phil Regulski Department of Atmospheric Sciences University of Washington February 12, 2008

2. 2 Overview Project Review Project Review Lightning Assimilation Technique Review Lightning Assimilation Technique Review Model Estimate Experiments Model Estimate Experiments Case Studies Case Studies December 2002 (Case 1 Review) December 2002 (Case 1 Review) October 2004 October 2004 November 2006 November 2006 In-progress/Future work In-progress/Future work

3. 3 Project Review Review Review Two working WRF-EnKF models Two working WRF-EnKF models LTNG2 – Original LTNG2 – Original Tested successfully on Dec. 2002 regime Tested successfully on Dec. 2002 regime LTNG4 – Minimal counting technique LTNG4 – Minimal counting technique Tested successfully on Dec. 2002 regime Tested successfully on Dec. 2002 regime

4. 4 Project Review Research Progress Research Progress Oct. 2004 Test Case - Analysis Oct. 2004 Test Case - Analysis Nov. 2006 Test Case - Analysis Nov. 2006 Test Case - Analysis Modifications to LTNG2 and LTNG4 models to improve analysis and forecasts Modifications to LTNG2 and LTNG4 models to improve analysis and forecasts In-progress In-progress Forecast analysis of Oct. 2004 Test Case Forecast analysis of Oct. 2004 Test Case Forecast analysis of Nov. 2006 Test Case Forecast analysis of Nov. 2006 Test Case 1-hr assimilation of cumulative convective rain rate data (previously using 6-hr cumulative totals) for LTNG2 and LTNG4 models 1-hr assimilation of cumulative convective rain rate data (previously using 6-hr cumulative totals) for LTNG2 and LTNG4 models

5. 5 Lightning Assimilation Techniques How model assimilates lightning: LTNG2 Original Lightning Experiment (LTNG2) Original Lightning Experiment (LTNG2) NLDN/LR lightning strike is detected NLDN/LR lightning strike is detected Lightning strike is converted into lightning rate from nearby LTNG observations Lightning strike is converted into lightning rate from nearby LTNG observations Lightning rate converted into convective rainfall rate using Pessi/Businger convective rain rate/lightning rate relationship Lightning rate converted into convective rainfall rate using Pessi/Businger convective rain rate/lightning rate relationship Relaxed WRF-EnKF quality control accepts more lightning strike convective rainfall values when comparing to background forecasts Relaxed WRF-EnKF quality control accepts more lightning strike convective rainfall values when comparing to background forecasts Convective rainfall (mm) is assimilated into WRF-EnKF Convective rainfall (mm) is assimilated into WRF-EnKF Successful testing on Dec. 2002 case Successful testing on Dec. 2002 case Apply to other test case events Apply to other test case events Test model adjustments to improve performance Test model adjustments to improve performance

6. 6 Lightning Assimilation Techniques How model assimilates lightning: LTNG4 Minimal Counting Technique Lightning Experiment (LTNG4) Minimal Counting Technique Lightning Experiment (LTNG4) NLDN/LR lightning strike is detected NLDN/LR lightning strike is detected Lightning strike is converted into lightning rate from nearby LTNG observations Lightning strike is converted into lightning rate from nearby LTNG observations Once any nearby lightning strikes are used to calculate a lightning density they are no longer available as an assimilation point (although they are still used to calculate LTNG densities) Once any nearby lightning strikes are used to calculate a lightning density they are no longer available as an assimilation point (although they are still used to calculate LTNG densities) Lightning rate converted into convective rainfall rate using Pessi/Businger convective rain rate/lightning rate relationship Lightning rate converted into convective rainfall rate using Pessi/Businger convective rain rate/lightning rate relationship Relaxed WRF-EnKF quality control accepts more LTNG strike convective rainfall values when comparing to background forecasts Relaxed WRF-EnKF quality control accepts more LTNG strike convective rainfall values when comparing to background forecasts Convective rainfall (mm) is assimilated into WRF-EnKF Convective rainfall (mm) is assimilated into WRF-EnKF Successful testing on Dec. 2002 case Successful testing on Dec. 2002 case Apply to other test case events Apply to other test case events Test model adjustments to improve performance Test model adjustments to improve performance

7. 7 Model Estimate Experiments Can we further improve Dec 2002 performance? Model-estimate and observations of cumulative convective precipitation calculated by LTNG density occasionally have large innovations leading to large increments in the model’s dynamical fields, possibly leading to locally unbalanced states Model-estimate and observations of cumulative convective precipitation calculated by LTNG density occasionally have large innovations leading to large increments in the model’s dynamical fields, possibly leading to locally unbalanced states Set a upper bound on assimilated cumulative convective precipitation Set a upper bound on assimilated cumulative convective precipitation Minimal Counting Technique Lightning Experiment (LTNG4) w/ modifications (LTNG5) Minimal Counting Technique Lightning Experiment (LTNG4) w/ modifications (LTNG5) Same techniques as LTNG4 with upper bound (18mm) Same techniques as LTNG4 with upper bound (18mm) Less improvement in analysis and forecasts Less improvement in analysis and forecasts Original LTNG4 still best performing model to test further on new regimes Original LTNG4 still best performing model to test further on new regimes Original Lightning Experiment (LTNG2) w/ modifications (LTNG6) Original Lightning Experiment (LTNG2) w/ modifications (LTNG6) Same techniques as LTNG2 with upper bound (18mm) Same techniques as LTNG2 with upper bound (18mm) Less improvement in analysis and forecasts Less improvement in analysis and forecasts Original LTNG2 still best performing model to test further on new regimes Original LTNG2 still best performing model to test further on new regimes Another solution Another solution Reduce cumulative value of convective rain assimilated from 6- to 1-hr block Reduce cumulative value of convective rain assimilated from 6- to 1-hr block(In-progress)

8. 8 Case Studies (Case 1 Review) Case #1: December 16-21, 2002 Case #1: December 16-21, 2002 Analysis Analysis Extra-tropical cyclone minimum SLP with new modifications Extra-tropical cyclone minimum SLP with new modifications SLP fields SLP fields WRF-EnKF v. Observations WRF-EnKF v. Observations

9. 9 Case Study #1 – December 2002 Minimum SLP recorded at extra-tropical cyclone’s center Limiting upper bound of cumulative convective precipitation degrades analysis performance (LTNG5/6)

10. 10 Case Study #1 – December 2002 SLP Analysis Fields Correct location and intensity of SLP cyclone center for LTNG assimilations

11. 11 Case Study #1 – December 2002 WRF-EnKF v. Observations: Integrated Error of SLP LTNG assimilation reduces error over control

12. 12 Case Studies Case #2: October 4-7, 2004 Case #2: October 4-7, 2004 Analysis Analysis Extra-tropical cyclone minimum SLP Extra-tropical cyclone minimum SLP SLP, H500 fields SLP, H500 fields WRF-EnKF v. Observations WRF-EnKF v. Observations Number of LTNG strikes during test case is much smaller than Dec. 2002 case Number of LTNG strikes during test case is much smaller than Dec. 2002 case

13. 13 Case Study #2 – October 2004 Minimum SLP recorded at extra-tropical cyclone’s center LTNG assimilated from 04/00 – 07/18 LTNG4 more accurately simulates min. SLP depth of extra tropical cyclone

14. 14 Case Study #2 – October 2004 SLP Analysis Fields Correct location and intensity of SLP cyclone center for LTNG assimilations

15. 15 Case Study #2 – October 2004 H500 Analysis Fields Correct location and intensity of H500 center for LTNG assimilations

16. 16 Case Study #2 – October 2004 H500 Analysis Fields LTNG4 pulls location of upper-level cyclone center too close to LTNG observations Reducing to 1-hr cumulative convective rain totals could weigh OBS correctly

17. 17 Case Study #2 – October 2004 WRF-EnKF v. Observations: Integrated Error of SLP LTNG assimilated from 04/00 – 07/18

18. 18 Case Study #2 – October 2004 WRF-EnKF v. Observations: Cloud top temperature v. Satellite LTNG2: 10/08 00

19. 19 Case Study #2 – October 2004 WRF-EnKF v. Observations: Cloud top temperature v. Satellite LTNG4: 10/08 00

20. 20 Case Studies Case #3: November 8-12, 2006 Case #3: November 8-12, 2006 Analysis Analysis Extra-tropical cyclone minimum SLP Extra-tropical cyclone minimum SLP SLP, H500 fields SLP, H500 fields WRF-EnKF v. Observations WRF-EnKF v. Observations

21. 21 Case Study #3 – November 2006 Minimum SLP recorded at extra-tropical cyclone’s center Only LTNG assimilated hours

22. 22 Case Study #3 – November 2006 SLP Analysis Fields Correct location and intensity of SLP cyclone center for LTNG assimilations

23. 23 Case Study #3 – November 2006 H500 Analysis Fields Correct location and intensity of H500 center for LTNG assimilations

24. 24 Case Study #3 – November 2006 WRF-EnKF v. Observations: Integrated Error of SLP LTNG assimilated from 08/00 – 11/18

25. 25 Case Study #3 – November 2006 WRF-EnKF v. Observations: Cloud top temperature v. Satellite LTNG2: 11/10 12

26. 26 Case Study #3 – November 2006 WRF-EnKF v. Observations: Cloud top temperature v. Satellite LTNG4: 11/10 12

27. 27 In-progress/Future Work In-Progress In-Progress Reduce WRF cumulative convective precipitation assimilation from 6- to 1-hr to avoid unbalanced states Reduce WRF cumulative convective precipitation assimilation from 6- to 1-hr to avoid unbalanced states 24-hr Forecasts for Oct 2004 Case 24-hr Forecasts for Oct 2004 Case 24-hr Forecasts for Nov 2006 Case 24-hr Forecasts for Nov 2006 Case Investigate robustness of Pessi/Businger lightning rate/convective rain rate relationship Investigate robustness of Pessi/Businger lightning rate/convective rain rate relationship Future Work Future Work Test Case #4 – December 2006 Test Case #4 – December 2006 Implement UW-ATMS lightning rate/convective rain rate relationship Implement UW-ATMS lightning rate/convective rain rate relationship Investigate lightning/graupel relationship Investigate lightning/graupel relationship Questions/Comments? Questions/Comments?